Dog spikes are utilized with timber sleepers for fastening a rail thereto, but of course these are not suitable for use with concrete or steel sleepers, and the most commonly utilized device with the latter is a rod formed from high carbon steel to a configuration such that when inserted in an aperture in a shoulder projecting from a sleeper, the rod imparts a pressure against the upper surface of the rail foot holding the rail flange in position against the sleeper. When the sleeper is a steel sleeper, loops are sometimes formed in the sleeper for reception of the rod and retain the rod to the steel sleeper.
A number of difficulties however are encountered with this type of securing device. Firstly in the case of the steel sleeper the sleeper surface is weakened by the incisions made therein for receiving the rod. Secondly, the pressure between the foot of the rail and the sleeper is subject to considerable variation. Thirdly, the resilience of the rod does not give a positive location of the rail with respect to the sleeper and a slight variation in gauge becomes possible. In order to avoid this, sometimes it has been deemed necessary to utilize spacing pieces between the shoulders and the rail flange. Still further, the pressure is applied along a line contact between the rod and the foot of the rail, resulting in a very high bearing pressure which is deleterious to insulating material and makes electrical insulating difficult. If the rod is used in conjunction with a bracket welded to a steel sleeper most of the above difficulties still remain, excepting that the incisions in the sleeper are avoided.
Other fixings include clips holding down the foot of the rail and tightened by nuts which engage bolts. However the nuts loosen in some instances, and the bolt apertures weaken the sleepers. Furthermore, positioning of the bolts from beneath the sleepers is sometimes difficult. The U.S. Pat. No. 2,040,824 discloses such an arrangement.
In a slight variation of the above, bolts are used which threadably engage sleeper inserts, but these are also subject to a danger of loosening. An example of this type of structure is illustrated and described in the Australian Pat. No. 460,983 (Tetsudo Kizai Kogyo Company Limited).
Prior art also includes a number of proposals utilizing spring plates for retaining a rail to a sleeper. Thus in the U.S. Pat. No. 1,995,020 issued to Woodings there is disclosed a spring plate adapted to be driven into engagement with retention means in a lateral direction. However release of such a plate is difficult unless special equipment is used. Similar comments also apply to the U.S. Pat. No. 1,925,124 issued to Warr, wherein a tail of the plate engaged a recess in a tie plate.
The closest prior art known to the Applicants is disclosed in the now lapsed Australian Patent Application No. 25398/71 of the British Railways Board. In the specification of that patent there is disclosed a spring plate which can engage the upper surface of an insulating pad with two bearing portions, and damage to the pad due to excess bearing pressure is avoided. However assembly is still slow, or alternatively requires use of special equipment, for example to deflect the spring plate while a cross pin is inserted. The disclosure does not include means whereby the plate is easily deflected by driving a retaining pin into position, nor means whereby the tail of the plate is free to move laterally with respect to a rail (for example upon deflection of the plate). In contrast, the cleat is located by its tail. Furthermore the very considerable lateral forces imposed upon the fastening is directly resisted by a part fixed in the foundation which also retains a plate engaging pin. The absence of resilience may have a deletorious effect on such a part or the concrete surrounding it, which can be subject to considerable damage.